1. Field of the Invention
This invention pertains to a distributed-power-generation system using a fuel cell and a method of controlling the same, and more particularly, to a distributed-power-generation system using a fuel cell that maintains a required rotation speed of a rotation axis related to the operation of power generation, and a method of controlling the same.
2. Description of the Related Art
A conventional distributed-power-generation system using a fuel cell produces DC power through a chemical reaction of the fuel cell and by rectifying three-phase power produced by a generator embedded therein. The conventional distributed-power-generation system converts the DC power obtained from the two kinds of power sources into AC power having a frequency of 50 Hz to 60 Hz using an inverter, and supplies the AC power for a three-phase power system.
A high-temperature gas is produced as a by-product by the chemical reaction of the fuel cell. The conventional distributed-power-generation system supplies power necessary for supplying air to the fuel cell using the high-temperature gas and provides the generator with a rotation power. That is, the conventional distributed-power-generation system provides a turbine connected to the rotation axis of a compressor and the generator with the high-temperature gas produced by the fuel cell while operating the compressor and the generator, thereby increasing energy efficiency.
In the conventional distributed-power-generation system using the fuel cell, the rotation speed of the generator depends on the volume of gas provided to the turbine. Also, the power efficiency of the generator varies according to the volume of the high-temperature gas that is produced by the fuel cell and provided to the turbine. An operation point of the conventional distributed-power-generation system using the fuel cell and the generator that rotates at high speed changes. As the volume of the high-temperature gas that rotates the turbine changes, it is impossible to operate the distributed-power-generation system while maintaining the power efficiency of the fuel cell. Also, since the power efficiency of the generator that rotates at high speed changes, it is difficult to maintain the optimum efficiency of the distributed-power-generation system.
The compressor containing an impeller that rotates at high speed goes through a variety of vibration modes from the time it starts to operate until it reaches a predetermined operation point, or when it moves from the predetermined operation point having a required speed to another operation point having a different speed. A variable operation of the distributed-power-generation system using the generator that rotates at high speed makes it impossible to avoid vibration when the operation point of the distributed-power-generation system changes. Thus, a distributed-power-generation system capable of maintaining a required speed is greatly required along with a method of controlling the system.